This invention relates to tricycles and in particular to tricycles having a single, manually driven rear wheel.
A variety of drives, including pedal drives have been known in the past for driving bicycles and tricycles, usually by means of a person's legs. Many of the known systems are not in common use either because they are generally too expensive to manufacture or maintain or they are not very reliable. The well known chain drive system used on most bicycles is generally reliable but this system is not very efficient, particularly when used by a normal or amateur cyclist who only pushes down on the pedals. The maximum theoretical efficiency where the cyclist only uses a pushing effort on the pedals is 64%.
Although tricycles are well known, they are commonly only in use by small children who do not have the ability to handle a bicycle yet. One advantage of a tricycle is that it is able to stand up on its own normally without balancing skills or the use of any kickstand or other form of support. A major difficulty with the common tricycle is that it is not able to travel at a high rate of speed, that is, a speed comparable to a standard bicycle. One reason why a tricycle is not built to travel at higher speeds is that the normal tricycle is unable to maneuver quickly around corners or curves. Unlike a bicycle, a tricycle can not be "leaned" into a curve to compensate for the centrifugal forces acting on it as the tricycle maneuvers the curve.
U.S. Pat. No. 3,820,820 issued June 28, 1974 to John Kutz describes a pedal drive for a bicycle wherein each of the two pedals is mounted upon an endless chain which defines the path of the pedal. The two pedal chains move along upright, generally oblong paths between upper and lower sprockets of the same size. The pedals are attached to the chains to move in opposition. A third endless chain transmits power from the pedal drive to the rear wheel. The difficulty with this known system is that at higher pedalling speeds, the rider's feet will have to undergo relatively quick lateral movements at the top and bottom ends of the pedal paths. The pedals will tend to move laterally from under the inertially slowed feet so that the rider may be uncomfortable with the movement of his feet. Also this known pedal drive under heavy thrust loads may suffer from the chains tending to run off the sprockets. This problem is aggravated by the need for the frame, linkages and connections to be light, individually rigid, durable and relatively inexpensive in a vehicle of this type.
U.S. Pat. No. 4,088,199 issued May 9, 1978 to W. Trautwein describes a three wheeled motorcycle having two steerable front wheels and a driven rear wheel. The front wheels are interconnected with a conventional motorcycle frame by a parallelogram configured coupling assembly utilizing a pair of cross members pivotally connecting hubs of the front wheels. The vehicle also comes with a locking bar that is pivotally supported on a foot rest and that can be used to prevent tipping of the vehicle. A rider may apply a stabilizing force for holding the vehicle upright while stopped and while operating at low speeds without contacting the ground. Also he may effect a banking operation by leaning and applying a force by one of his feet to a portion of the foot resting platform on one side of the vehicle. There is no suggestion in the patent that the design could be used for a tricycle and indeed the design appears impractical for this purpose.
U.S. Pat. No. 4,072,325 issued Feb. 7, 1978 to Bright Engineering, Incorporated describes a three wheeled vehicle having two steerable front wheels. It is equipped with a device for automatically stabilizing the vehicle against the effects of transverse acceleration forces and roll movements, due to turning maneuvers by means of an on-board pendulum. As shown in FIGS. 8 and 9, the vehicle is able to assume a leaning attitude while negotiating a turn either on a level road bed or on a banked road bed. The vehicle is said to have improved stability due to the concentration of a large part of the mass of the vehicle, including the operator and the passenger if any, in the suspended pendulum element of the vehicle. The approach taken in this patent is not practical for a bicycle or tricycle design wherein the total vehicle weight might be as much as 45 pounds with the centre of mass two feet above the road and the weight of the operator, the average weight of whom is 170 pounds, is centered at least three feet above the road.
It is an object of the present invention to provide a pedal drive for a multiwheel vehicle that is quite efficient at converting the pedalling power provided by an operator into mechanical, rotational power able to drive the vehicle.
It is a further object of the present invention to provide a tricycle that is able to negotiate a curve at reasonably high speed by being "leaned" into the curve to compensate for the centrifugal forces acting on the tricycle.